Bader’s analysis of the electron density in the Pbca enstatite – Pbcn protoenstatite phase transition

Abstract

The Bader’s topological analysis of the electron density obtained via ab initio quantum mechanical simulation at Hartree–Fock and DFT level has been performed for experimentally in situ heated structures of enstatite–protoenstatite MgSiO3. The measurements have been performed in the temperature range 1200–1400 K. The work was aimed at characterizing both the evolution of the electron arrangement in the crystal and that of the crystal-structure at the enstatite–protoenstatite phase transition in terms of topology of the electron density, with particular care about the Mg–O and the O–O bonds. The observed breaking of some chemical bonds with increasing temperature and/or due to the phase transformation have been explained, for the first time, in the light of a topological mechanism based on the Catastrophe Theory applied to the framework of the Bader’s theory.